As Allan Karlsson (Robert Gustafsson, the Swedish Harry Enfield) approaches his centenary, he decides to bust out of the old folks home and take the next train out of town. An encounter with a skinhead at the station leaves our elderly hero in possession of a suitcase – a MacGuffin that various menacing gang members will chase for the rest of the movie.

Meanwhile, Allan will acquire his own makeshift gang, including a nervous, indecisive young academic, a burly stationmaster, and a lady with an elephant. Mostly, he reminisces: a stream of tall-tale recollections that casts him as an alternative Forrest Gump.

Allan Karlsson, we soon learn, has gotten drunk with both Franco and Stalin (on different occasions, obviously), and has spent time in the company of Robert Oppenheimer, Harry S Truman, Ronald Reagan and Albert Einstein’s fictional idiot brother, Herbert.

There are many cartoon explosions in this pathologically whimsical screen adaptation of Jonas Jonasson’s internationally bestselling novel of the same name (Hundraåringen som klev ut genom fönstret och försvann). These sometimes fatal pyrotechnics form a kind of punctuation mark and also set the strange tone: think gallows humour with banana skin- brand slapstick.

Chances are, the viewer’s taste for zaniness will be exhausted long before the film’s is. But if you keep pace with the relentless wackiness, this is plenty entertaining. Between Matti Bye’s carnivalesque score, Göran Hallberg’s colourful lensing and the likeably quirky players, you couldn’t say there was a dull moment.

Alan Ford’s Bali-dwelling hoodlum adds still more pile to this shaggy dog story. Can a geriatric action hero take on Transformers 4 and win? Box office receipts from Scandinavia suggest as much. Go, you crazy centenarian, go.